10,260 research outputs found
Knowledge Does Not Fall Far from the Tree - A Case Study on the Diffusion of Solar Cells in Germany
The purpose of this paper is to illuminate the geographical diffusion of photovoltaic installations in Germany quantitatively and to test if preexisting photovoltaic systems stimulate further installations nearby; thus we investigate to which extent knowledge flows depend on geographic proximity. We develop an econometric model, which is discrete in time and space, but the level of geographical agglomeration is adjustable in arbitrarily small steps. We find that the probability to install a photovoltaic system dependents on the geographic proximity to agents, who have previously installed a photovoltaic system. In conclusion, our results confirm that knowledge exchange attenuates with distance.
Leptoquark Pair Production at Colliders
The pair production cross section for scalar and vector leptoquarks at
colliders is calculated for the case of photon--gluon fusion. In a model
independent analysis we consider the most general and conserving
couplings of gluons and photons to both scalar and vector leptoquarks described
by an effective low--energy Lagangian which obeys
invariance. Numerical predictions are given for the kinematical regime at HERA
and LEP~~LHC.Comment: 15 p., postscript encoded with uufiles; DESY 94--07
Interaction of modulated pulses in the nonlinear Schroedinger equation with periodic potential
We consider a cubic nonlinear Schroedinger equation with periodic potential.
In a semiclassical scaling the nonlinear interaction of modulated pulses
concentrated in one or several Bloch bands is studied. The notion of closed
mode systems is introduced which allows for the rigorous derivation of a finite
system of amplitude equations describing the macroscopic dynamics of these
pulses
High-frequency averaging in semi-classical Hartree-type equations
We investigate the asymptotic behavior of solutions to semi-classical
Schroedinger equations with nonlinearities of Hartree type. For a weakly
nonlinear scaling, we show the validity of an asymptotic superposition
principle for slowly modulated highly oscillatory pulses. The result is based
on a high-frequency averaging effect due to the nonlocal nature of the Hartree
potential, which inhibits the creation of new resonant waves. In the proof we
make use of the framework of Wiener algebras.Comment: 13 pages; Version 2: Added Remark 2.
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